Download 40 -2 THE IMMUNE SYSTEM

40 -2 THE IMMUNE SYSTEM
Immune System – Complex, infection fighting part of body.
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Includes WBCs, Bone Marrow, Lymph system
Immunity (protection) – The ability of the body to defend itself against pathogens
• Pathogens – Any disease carrying organisms.
3 LINES OF DEFENSE
2 Non-specific Defenses
1. Physical / Chemical barriers – Physical - Skin, lining of body passages, mucus.
Chemical – Sweat, tears, saliva stomach acid.
If pathogen gets through 1st line and starts infection
2. Inflammatory Response - Swelling, warmth and redness as blood rushes to infected site bringing
Phagocytes (WBCs) that engulf damaged cells and bacteria.
Pus – WBCs that have engulfed bacteria and damaged cells.
Interferon – Proteins produced by cells that block virus reproduction.
Fever – Raises body temperature & heart rate to destroy pathogens and increase WBC rate
of response.
Specific Defense
3. Immune Response – A series of specific defenses designed to attack a particular pathogen.
Antigen – A foreign protein ID) that triggers an immune response.
Lymphocytes – WBCs in body that recognize and destroy antigens.
B Cells & T Cells are produced in bone marrow. B cells mature in Bone marrow while
T cells mature in Thymus gland. At maturity, both are released in Circ & Lymph System.
Antibodies – Y shaped proteins made to attract & bind to antigens on pathogen surfaces.
I. Humoral Immunity – B cells in plasma that fight Bacterial invasion in blood by producing antibodies
and remembering how in the future.
1. Macrophage (giant WBC) engulfs Bacteria.
2. Macrophage displays foreign antigen on its surface.
a) B cells “learn” how to defeat antigen and produce two cells.
b) Plasma Cells - make antibodies that bind to antigens, destroying them.
Memory Cells – Remembers antibodies made for faster future response.
II. Cell- Mediated Immunity – T cells in body used to fight Virus in healthy cells.
1. Macrophage engulfs Virus.
2. Macrophage displays foreign antigen on its surface.
3. T Cells produce different T cells including
a) Killer T Cells – Bind to infected cells membranes, destroying them.
b) Memory Cells - Remembers antibodies made for faster future response.
Recipients of transplanted organs trigger an immune response. Donate organs with similar protein Ids
trigger less response but recipients must take immune suppression drugs for life.
ACQUIRING IMMUNITY
Active Immunity – Acquired by exposure to the pathogen which triggers immune defenses.
Vaccination – Injecting a weakened form of the disease to start defenses early.
Passive Immunity – Getting outside antibodies to temporarily fight disease.
Ex – Mother’s milk to baby, rabies vaccine.
IMMUNE RESPONSE TIMES
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Primary Immune Response – Antigen enters body for first time. First 5 days no increase in WBCs “Body
is learning.” 10-15 days gradual rise in WBCs.
Secondary Immune Response - Same Antigen enters months/years later. Within 1-2 days, rapid increase
in WBCs.